57 plate Mondeo.

Have 2 keys for it, one usually sits in a drawer as a spare.

In the last week, the main key for it has stopped unlocking/locking remotely.  I've changed the batteries in it and it still didn't work.

Until I used the spare to remotely unlock it, then the first key started working again.   Lock/unlock no problem.

After a period of time it seems to reset and the main key doesn't work again until the second one is used.

Once in the car, both keys start it without any issue.

 

I'd rather not have to take the spare with me every time I go out as it negates the point of a spare if one gets lost!

 

Anyone else seen this behaviour before??

2 hours ago, AntsMondeo said:

Anyone else seen this behaviour before??

Frequently when the replacement battery is of poor quality. Use Energizer and buy it only from a reputable source. Check the new replacement battery with a multimeter and make sure it is 3.30V 

Yes, something similar. I posted about it at the time, but I had a replacement fail within days, despite it being a supposedly new genuine Duracell from a reputable source. I always check the voltage as Unofix suggests, but it went from 3.3v to under 2 in a couple of days.

There have been reports of fakes (especially Duracell, as it's a big name) getting into even legitimate supply chains, so it could have been that, or just an unlucky "dud".

I've used Energizer since.